Conventional polycrystalline diamond compact (PDC) cutting elements include a cutting table and a substrate. The substrate conventionally comprises a metal material, such as tungsten carbide, to enable robust coupling of the PDC cutting elements to a bit body. The cutting table typically includes randomly oriented, mutually bonded diamond (or, sometimes, cubic boron nitride (CBN)) particles that have also been adhered to the substrate on which the cutting table is formed, under extremely high-temperature, high-pressure (HTHP) conditions. Cobalt binders, also known as catalysts, have been widely used to initiate bonding of superabrasive particles to one another and to the substrates. Although the use of cobalt in PDC cutting elements has been widespread, PDC cutting elements having cutting tables that include cobalt binders are not thermally stable at the typically high operating temperatures to which the cutting elements are subjected due to the greater coefficient of thermal expansion of the cobalt relative to the superabrasive particles and, further, because the presence of cobalt tends to initiate back-graphitization of the diamond in the cutting table when a temperature above about 750° C. is reached. As a result, the presence of the cobalt results in premature wearing of and damage to the cutting table.
A number of different approaches have been taken to enhance the thermal stability of polycrystalline diamond and CBN cutting tables. One type of thermally stable cutting table that has been developed includes polycrystalline diamond sintered with a carbonate binder, such as a Mg, Ca, Sr, or Ba carbonate binder. The use of a carbonate binder increases the pressure and/or temperature required to actually bind diamond particles to one another, however. Consequently, the diameters of PDC cutting elements that include carbonate binders lack an integral carbide support or substrate and are typically much smaller than the diameters of PDC cutting elements that are manufactured with cobalt.
Another type of thermally stable cutting table is a PDC from which the cobalt binder has been removed, such as by acid leaching or electrolytic removal. Such cutting elements have a tendency to be somewhat fragile, however, due to their lack of an integral carbide support or substrate and, in part, due to the removal of substantially all of the cobalt binder, which may result in a cutting table with a relatively low diamond density. Consequently, the practical size of a cutting table from which the cobalt may be effectively removed is limited.
Yet another type of thermally stable cutting table is similar to that described in the preceding paragraph, but the pores resulting from removal of the cobalt have been filled with silicon and/or silicon carbide. Examples of this type of cutting element are described in U.S. Pat. Nos. 4,151,686 and 4,793,828. Such cutting tables are more robust than those from which the cobalt has merely leached, but the silicon precludes easy attachment of the cutting table to a supporting substrate.